The invention relates to a RF switch matrix and, more particularly, the invention relates to an integrated RF Mxc3x97N switch matrix using Nxc3x97N switch modules.
Switch matrices are critical components in virtually all modern communications systems, especially satellite systems. Such matrices are used principally to route up-link channels to a specific down-link channel. In some instances, switch matrices may have a xe2x80x9cbroadcast modexe2x80x9d in that an individual incoming signal is simultaneously routed to a number of outgoing channels for transmission.
RF switches come in a variety of configurations, the most basic being a single pole, single throw having a single RF input and a single RF output. Typically the RF signal is switched electronically with RF switching diodes or field effect transistors. Such RF switches are combined to form Mxc3x97N switch matrices and are typically constructed using Monolithic Microwave Integrated Circuitry (MMIC) techniques wherein nonintersecting transmission lines, interconnections, and switch elements are integrated on a multilevel substrate using thin film processing techniques. The MMIC technique is impractical in most instances where there are numerous inputs and outputs to be switched because chip size becomes very large due to circuit complexity.
Thus, there exists a need in the art for automated production of efficient, reliable switch matrices that are able to operate in the RF frequency range.
The disadvantages associated with the prior art are overcome by forming an Mxc3x97N RF switch matrix using a multilayer ceramic circuit board that accommodates Mxc3x97N switch modules, each switch module being an Nxc3x97N switch matrix. The ceramic structure exhibits low RF loss and the metal base functions both as a heatsink and as a RF ground. The circuit board has an Mxc3x97N array of mounting sites for accepting the switch modules and contains all the necessary RF routing, bias, and control lines to interconnect the switch modules to from the Mxc3x97N switch matrix.
In one embodiment of the invention, the circuit board is a multilayer ceramic structure on a metal base that is fired using a Low Temperature Ceramic Circuit on Metal (LTCC-M) process. An LTCC-M process provides for zero-shrinkage in the plane of the circuit board allowing for the fabrication of large-area boards with tight tolerances over the entire area of the board. The switch modules can be MMIC devices or can also be fabricated using an LTCC-M process. The switch modules attach to the ceramic circuit board at the mounting sites via wire-bonds or flip-chip bonds. The mounting sites are punch cavities whereby the metal base of each switch module is coupled to the metal base of the motherboard. The switch modules are interconnected by the circuit board to from an Mxc3x97N switch matrix. In an alternative embodiment of the invention, the switch modules are surface mounted to the circuit board at the mounting sites.